Method of determining positive and negative polarity without a multimeter
Three simple and fast way to identify the positive and negative poles, of course, there are many ways to judge the positive and negative poles, not limited to these three, I hope it will help you, right?
The first method: electrolysis method
Electrolysis method
Electrolysis of water experiments we may have contacted in high school, if the water is electrified, in the cathode will produce hydrogen, and in the anode will produce oxygen, but the efficiency of this generation of hydrogen is relatively low, if we can find a catalyst, then the human energy will be completely solved! Today we will make good use of this knowledge, first of all, the power supply poles connected to the water (pure water can not be), by the principle of electrolysis of water can be seen in the production of gas more that pole is the power supply negative (hydrogen and oxygen ratio of 2:1), at the same time, the negative pole will also be corroded and a lot more than the anode is serious, according to the two points more able to fully determine the power supply positive and negative poles.
The second method: connect a LED test
Connect a LED of this method is relatively simple, but must be prepared to prepare some materials, relative to the first more difficult, but is considered the simplest circuit, the circuit only a LED and a current-limiting protection resistor, when the power supply to be tested is connected to both sides of the above components, if the LED is bright, that is, close to the end of the LED for the power supply is positive, the principle is very simple is the use of light-emitting diode Unidirectional conductivity.
The third method: design a simple circuit detection
Of course, in addition to the above two methods can also design a circuit to detect their own design may be more complex, but generally better results in their own design, we use the material has two LEDs also have a limited current resistor, according to our knowledge of the analysis can be seen, regardless of the power supply is connected to which two with the line, is always close to the positive end of the pole of the LED is bright as for the principle of and the second method, the use of light-emitting diodes Unidirectional conductivity of light-emitting diodes.
